The present invention relates to an ink-jet recording head, in which a piezoelectric element is formed via a vibration plate in a portion of a pressure generating chamber communicating with a nozzle orifice that ejects ink droplets, and ink droplets are ejected by displacement of the piezoelectric element. Furthermore, the present invention relates to a manufacturing method of the same and an ink-jet recording apparatus.
Two types of recording heads are put into practical use with regard to the ink-jet recording head, in which a portion of a pressure generating chamber communicating with a nozzle orifice that ejects ink droplets is constituted of a vibration plate, and the vibration plate is deformed by a piezoelectric element to pressurize ink in the pressure generating chamber, thus ink droplets are ejected from the nozzle orifice. One is a recording bead using a piezoelectric actuator of longitudinal vibration mode that expands and contracts in the axis direction of the piezoelectric element, and the other one uses a piezoelectric actuator of flexural vibration mode.
The former can change volume of the pressure generating chamber by abutting an end surface of the piezoelectric element against the vibration plate, and manufacturing of a head suitable to high density printing is enabled. On the contrary, a difficult process in which the piezoelectric element is cut and divided in a comb teeth shape to make it coincide with the array pitch of the nozzle orifice and a method so that the cut and divided piezoelectric element is aligned and fixed to the pressure generating chamber is necessary, thus there is a problem of a complex manufacturing process.
On the other hand, in the latter, the piezoelectric element can be fabricated and installed on a vibration plate by a relatively simple process in which a green sheet, which is piezoelectric material, is adhered while fitting the shape thereof to the pressure generating chamber shape and is sintered. However, a certain size of vibration plate is required due to the usage of flexural vibration, thus there is a problem that high density array of the piezoelectric elements is difficult.
In order to solve the disadvantage of the latter recording head, as shown in Japanese Patent Laid-Open No. Hei 5-286131, a recording head is proposed, in which an even piezoelectric material layer is formed across the entire surface of the vibration plate by a deposition technology, the piezoelectric material layer is cut and divided into a shape corresponding to the pressure generating chamber by a lithography method, and the piezoelectric element is formed so as to be independent of another piezoelectric element for each pressure generating chamber.
According to the above-described process, a work for adhering the piezoelectric element on the vibration plate is unnecessary, and there is an advantage that not only the piezoelectric element can be fabricated and installed by accurate and simple means, lithography method, but also the thickness of the piezoelectric element can be made thin and a high-speed drive is enabled.
In such an ink-jet printing head, in general, the pressure generating chamber is formed so as to penetrate in the thickness direction of the plate by performing etching for the plate by use of a specified mask pattern from the plate surface opposite that having the piezoelectric element made thereon.
However, in such an ink-jet recording head, an error sometimes occurs in aligning the mask pattern for forming the piezoelectric element and the mask pattern for forming the pressure generating chamber, alternatively slippage of light exposure sometimes occurs due to a warp or the like of the plate where the pressure generating chamber is formed. Therefore, there is a problem that the relative positional accuracy between the piezoelectric element and the pressure generating chamber is lowered.
Moreover, in the case, for example, where a single crystal silicon substrate of a plane (110) of the plane orientation is employed as a plate, a position of the pressure generating chamber, the position being close to the vibration plate, is not stable due to variation of the vertical degree of a plane (111) thereof. Therefore, the relative positional accuracy between the piezoelectric element and the pressure generating chamber is lowered, thus causing problems of low ink ejection characteristics and low stability thereof.
Furthermore, in the case where the pressure generating chambers are arrayed in a high density, the thickness of compartment walls between the pressure generating chambers is made thin which results in lack of rigidity of the compartment walls, thus causing the problem that cross talk occurs among the pressure generating chambers.
For example, in the piezoelectric actuator of longitudinal vibration mode, a structure is conceived, in which a wide width portion is provided in a portion of the pressure generating chamber, the portion being close to the vibration plate, and the width of portions of the pressure generating chamber other than the wide width portion is made narrow to thicken the corresponding compartment wall portions. However, in this case, an operation such as processing and pasting for the wide width portion of the pressure generating chamber is required, thus causing problems on operationality and accuracy.
In consideration of the foregoing circumstances, the object of the present invention is to provide an ink-jet recording head, in which the relative positional accuracy between the piezoelectric element and the pressure generating chamber is improved to make ink ejection characteristics and stability thereof improved, and the pressure generating chambers can be arrayed in a high density and further, cross talk between the pressure generating chambers can be reduced. Moreover, the object of the present invention is to provide a manufacturing method of the ink-jet recording head and an ink-jet recording apparatus.
A first aspect of the present invention for solving the above-described problems is an ink-jet recording head that comprises: a passage-forming substrate having a pressure generating chamber formed thereon, which communicates with a nozzle orifice; and a piezoelectric element formed of a thin film and by a lithography method via a vibration plate constituting a portion of the pressure generating chamber in a region corresponding to the pressure generating chamber. The ink-jet recording head is characterized in that the space portion communicating with the pressure generating chamber and having at least one surface constituted of the vibration plate is provided in a region opposite to the pressure generating chamber, which is between the passage-forming substrate and the vibration plate, and at least the width of the pressure generating chamber, which is close to the space portion, is equal to the width of the space portion or less.
In the first aspect, relative positional accuracy between the piezoelectric element and the pressure generating chamber, that is, a positional accuracy between the piezoelectric element and the vibration region of the vibration plate can be improved. In addition, the compartment wall between the pressure generating chambers can be made thicker to increase the rigidity, thus cross talk between the pressure generating chambers can be reduced.
A second aspect of the ink-jet recording head of the present invention according to the first aspect is characterized in that at least the width of the pressure generating chamber, which is close to the vibration plate, is approximately equal to the width of the space portion, and outer peripheries of both sides of the space portion in the width direction regulate the width of the pressure generating chamber.
In the second aspect, the relative positional accuracy between the pressure generating chamber and the piezoelectric element is improved, thus ink ejection characteristics are improved.
A third aspect of the ink-jet recording head of the present invention according to any one of the first and second aspects is characterized in that at least a portion of the side surface of the pressure generating chamber is constituted of a slanted surface slanting from the space portion to the inside of the pressure generating chamber.
In the third aspect, ink can be surely supplied to the pressure generating chamber and the space portion.
A fourth aspect of the ink-jet recording head of the present invention according to the third aspect is characterized in that the slanted surface includes an etching stop surface of the passage-forming substrate.
In the fourth aspect, the pressure generating chamber can be formed readily in high accuracy, and as a result, the side surface thereof becomes a slanted surface.
A fifth aspect of the ink-jet recording head of the present invention according to any one of the first to fourth aspects is characterized in that a passage-forming layer is provided between the passage-forming substrate and the vibration plate, and the space portion is formed so as to penetrate the passage-forming layer.
In the fifth aspect, the space portion can be formed readily in high accuracy.
A sixth aspect of the ink-jet recording head of the present invention according to the fifth aspect is characterized in that the passage-forming layer comprises boron-doped polysilicon.
In the sixth aspect, the space portion can be formed in the passage-forming layer readily in high accuracy.
A seventh aspect of the ink-jet recording head of the present invention according to any one of the first to fourth aspects is characterized in that the vibration plate has a step difference portion extending to a direction crossing with the plane direction in a region corresponding to each pressure generating chamber, and the space portion is defined by the step difference portion.
In the seventh aspect, since the space portion is defined by the step difference portion of the vibration plate, the space portion can be formed readily in high accuracy.
An eighth aspect of the ink-jet recording head of the present invention according to the seventh aspect is characterized in that a reinforcement layer, that is provided so as to be tightly attached to the step difference portion, is provided at least in a region corresponding to the outside of the space portion in the width direction.
In the eighth aspect, the strength of the step difference portion is increased by the reinforcement layer, thus a shake of the step difference portion in the plane direction and destruction accompanied with the shake are prevented.
A ninth aspect of the ink-jet recording head of the present invention according to the eighth aspect is characterized in that the reinforcement layer in the region corresponding to each side of the piezoelectric element in the width direction is extended to the upper portion of the step difference portion, which is close to the piezoelectric element, and the vibration region of the vibration plate is regulated by a gap between the reinforcement layers.
In the ninth aspect, the width of the vibration plate, actually vibrated by the drive of the piezoelectric element, can be appropriately adjusted.
A tenth aspect of the ink-jet recording head of the present invention according to any one of the eighth to ninth aspects is characterized in that the thickness of the reinforcement layer is thicker than height of the step difference portion of the vibration plate.
In the tenth aspect, the strength of the step difference portion is surely increased, thus a shake of the step difference portion in the plane direction and destruction accompanied with the shake are surely prevented.
An eleventh aspect of the ink-jet recording head of the present invention according to any one of the eighth to tenth aspects is characterized in that the reinforcement layer includes an uncontinuous piezoelectric layer that is uncontinuous with the piezoelectric layer of the piezoelectric element.
In the eleventh aspect, the reinforcement layer can be readily formed at the same time as performing patterning for the piezoelectric element.
A twelfth aspect of the ink-jet recording head of the present invention according to any one of the first to eleventh aspects is characterized in that the height of the space portion ranges from 0.1 xcexcm to 100 xcexcm.
In the twelfth aspect, the volume required for ink ejection can be obtained by the pressure generating chamber and the space portion.
A thirteenth aspect of the ink-jet recording head of the present invention according to the twelfth aspect is characterized in that the height of the space portion ranges from 1 xcexcm to 10 xcexcm.
In the thirteenth aspect, the pressure generating chamber and the space portion can be set so as to have a volume suitable for ink ejection.
A fourteenth aspect of the ink-jet recording head of the present invention according to any one of the first to thirteenth aspects is characterized in that an expanded portion having a width wider than the pressure generating chamber and wider than the nozzle orifice is provided in the vicinity of the nozzle orifice of the pressure generating chamber.
In the fourteenth aspect, ink can be well ejected even with the pressure generating chamber having a relatively narrow width.
A fifteenth aspect of the ink-jet recording head of the present invention according to any one of the first to fourteenth aspects is characterized in that the width of the space portion is wider than the width of the piezoelectric active portion constituting the piezoelectric element, and the relation between the width WA of the pressure generating chamber and the width WB of the piezoelectric active portion satisfies WA less than WB.
In the fifteenth aspect, the pressure generating chamber and the space portion can be set so as to have the volume required for ink ejection, and the rigidity of the compartment wall can be improved.
A sixteenth aspect of the ink-jet recording head of the present invention according to any one of the first to thirteenth aspects is characterized in that an insulation layer having an open portion in a region opposite to the pressure generating chamber is provided on a surface of the passage-forming substrate, the surface being opposite to the vibration plate, and a portion of the insulation layer projects into the region opposite to the pressure generating chamber.
In the sixteenth aspect, a portion of the insulation layer projects into the region opposite to the pressure generating chamber by forming the pressure generating chamber in the passage-forming substrate from the open portion of the insulation layer via the space portion.
A seventeenth aspect of the ink-jet recording head of the present invention according to any one of the first to sixteenth aspects is characterized in that the passage-forming substrate consists of a single crystal silicon substrate, and the pressure generating chamber is formed by anisotropic etching.
In the seventeenth aspect, the pressure generating chamber can be formed relatively readily and in high accuracy.
An eighteenth aspect of the ink-jet recording head of the present invention according to any one of the first to seventeenth aspects is characterized in that it comprises the ink-jet recording head specified in any one of the first to seventeenth aspects.
In the eighteenth aspect, the ink-jet recording apparatus having improved ink ejection characteristics of the head can be realized.
A nineteenth aspect of the present invention is a manufacturing method for an ink-jet recording head, which comprises: a passage-forming substrate having a pressure generating chamber formed thereon, which communicates with a nozzle orifice; and a piezoelectric element formed of a thin film and by a lithography method via a vibration plate constituting a portion of the pressure generating chamber in a region corresponding to the pressure generating chamber, in which a passage-forming layer is provided between the passage-forming substrate and the vibration plate, and the passage-forming layer has a space portion formed in a region opposite to the pressure generating chamber. The manufacturing method of an ink-jet recording head is characterized by comprising the steps of: forming the passage-forming layer on the passage-forming substrate and imparting etching selectivity to a region that will be the space portion of the passage-forming layer; forming the vibration plate on the passage-forming layer and forming a piezoelectric element on the vibration plate; and performing anisotropic etching for the passage-forming substrate from a surface opposite that having the passage-forming layer to form a penetrated portion at least to a region that will be the space portion of the passage-forming layer, etching the passage-forming layer to form the space portion, and forming a pressure generating chamber opposite the space portion.
In the nineteenth aspect, the pressure generating chamber can be formed readily and in high accuracy by forming the pressure generating chamber via the penetrated portion of the passage-forming substrate and the space portion of the passage-forming layer, and the width of the pressure generating chamber is regulated in high accuracy.
A twentieth aspect of the manufacturing method of an ink-jet recording head of the present invention according to the nineteenth aspect is characterized in that the passage-forming layer comprises polysilicon, and etching selectivity is imparted by doping boron onto a region other than the region that will be the space portion.
In the twentieth aspect, the space portion can be formed in high accuracy and the manufacturing process of the ink-jet recording head can be simplified.
A twenty-first aspect of the present invention is a manufacturing method for an ink-jet recording head, which comprises: a passage-forming substrate having a pressure generating chamber formed thereon, which communicates with a nozzle orifice; and a piezoelectric element formed of a thin film and by a lithography method via a vibration plate constituting a portion of the pressure generating chamber in a region corresponding to the pressure generating chamber, in which a passage-forming layer that consists of boron-doped polysilicon is provided between the passage-forming substrate and the vibration plate, and the passage-forming layer has a space portion formed in a region opposite to the pressure generating chamber. The manufacturing method of an ink-jet recording head is characterized in that it comprises the steps of: forming a polysilicon layer on the passage-forming substrate; doping boron onto a region other than a region in which the wide width portion of the polysilicon layer is formed to make the passage-forming layer; forming the vibration plate on the passage-forming layer and forming a piezoelectric element on the vibration plate; etching the passage-forming substrate from a surface opposite that having the passage-forming substrate to form the pressure generating chamber; and entirely etching the region of the polysilicon layer other than the region having boron doped thereon from the pressure generating chamber to form the space portion.
In the twenty-first aspect, the space portion can be readily formed and in high accuracy by removing the polysilicon layer by etching.
A twenty-second aspect of the manufacturing method of an ink-jet recording head of the present invention according to the twenty-first aspect is characterized in that the step of forming the pressure generating chamber and the step of forming the space portion are continuously performed.
In the twenty-second aspect, the space portion can be formed in high accuracy, and the manufacturing process of the ink-jet recording head can be simplified.